It is known to tag petroleum products with markers, as for example as taught in U.S. Pat. Nos. 4,209,302 and 4,735,631, the teachings of each of which are incorporated herein by reference.
A dye is defined herein as a material lending visible color when dissolved in the dyed product. Examples of dyes which have been used for dyeing organic liquids are Color Index Solvent Red #24, Solvent Red #19, Solvent Yellow #14, Solvent Blue #36, and Solvent Green #3.
A marker is defined herein as a substance which can be dissolved in a liquid to be identified, then subsequently detected by performing a simple chemical or physical test on the tagged liquid. Markers that have been proposed, or are in use, include furfural, quinizarin, diphenylamine and radioactive materials. (Radioactive materials have not been accepted in Western countries because of special equipment and precautionary measures associated with their handling.)
Dyes and markers are needed to clearly distinguish chemically or physically similar liquids As one example, fuels are dyed or tagged to provide visually distinctive brand and grade denominations for commercial and safety reasons. As another example, some lightly taxed products are dyed or tagged to distinguish them from similar materials subject to higher taxes. Furthermore, certain fuels are dyed or tagged to deter fraudulent adulteration of premium grade products with lower grade products, such as by blending kerosene, stove oil, or diesel fuel into regular grade gasoline or blending regular grade gasoline into premium grade gasoline. Identification of particular batches of bulk liquids for protection against theft is another valuable function of markers and dyes, particularly for identifying fuels owned by large government, military or commercial consumers. Finally, marketers of brand name products dye or tag their products to detect substitution of others' products in their distribution system.
Dyes alone are not always adequate to securely and reliably identify liquids. Many dyes are easily removed by unauthorized persons. Furthermore, dyes can be obscured by other natural or added substances (particularly dyes present at low concentrations in a mixture of fuels). Because dyes alone have these shortcomings, a combination of a dye and a marker often is used to tag fuel.
Above-referenced U.S. Pat. No. 4,735,631 recites important characteristics of certain desirable markers for petroleum include:
1. are entirely foreign to the liquids; PA1 2. can be supplied as highly concentrated solutions in compatible solvents; PA1 3. are easily detected by a simple field test; PA1 4. are not obscured by unstable natural components of the liquids; PA1 5. are stable over the anticipated storage life of the tagged liquid (usually three to six months); and PA1 6. have identities which can be confirmed by laboratory methods.
The markers of the present invention are preferably used at such concentrations and in such manner that they cannot be observed in the petroleum product until appropriately extracted in concentrated form from the petroleum product. If used at concentrations of less than about 10 ppm, the markers impart almost no detectable color, even to a clear, colorless petroleum product. If used in a naturally yellow petroleum product, the observable effect, if any, of the marker is that of a blue whitner, brightening the petroleum product. The marker will be totally obscured by any dye used to impart a color to the petroleum product.
Markers of the present invention are also advantageous is that they provide quantitative determinations. Most markers are adequate for detection of their presence in petroleum product; however, many available markers do not provide a good quantitative measurement of their levels in liquid petroleum products. Quantitative determinations are particularly important in cases where dilution is suspected, e.g., dilution of a higher-taxed fuel with a lower-taxed fuel.